Add value_from_statisics to AggregateUDFImpl, remove special case for min/max/count aggregate statistics

datafusion/expr/src/lib.rs

@@ -90,7 +90,7 @@ pub use logical_plan::*;
 pub use partition_evaluator::PartitionEvaluator;
 pub use sqlparser;
 pub use table_source::{TableProviderFilterPushDown, TableSource, TableType};
-pub use udaf::{AggregateUDF, AggregateUDFImpl, ReversedUDAF};
+pub use udaf::{AggregateUDF, AggregateUDFImpl, ReversedUDAF, StatisticsArgs};
 pub use udf::{ScalarUDF, ScalarUDFImpl};
 pub use udwf::{WindowUDF, WindowUDFImpl};
 pub use window_frame::{WindowFrame, WindowFrameBound, WindowFrameUnits};

datafusion/expr/src/udaf.rs

@@ -25,7 +25,8 @@ use std::vec;
 
 use arrow::datatypes::{DataType, Field};
 
-use datafusion_common::{exec_err, not_impl_err, Result, ScalarValue};
+use datafusion_common::{exec_err, not_impl_err, Result, ScalarValue, Statistics};
+use datafusion_physical_expr_common::physical_expr::PhysicalExpr;
 
 use crate::expr::AggregateFunction;
 use crate::function::{
@@ -93,6 +94,19 @@ impl fmt::Display for AggregateUDF {
     }
 }
 
+pub struct StatisticsArgs<'a> {
+    pub statistics: &'a Statistics,
+    pub return_type: &'a DataType,
+    /// Whether the aggregate function is distinct.
+    ///
+    /// ```sql
+    /// SELECT COUNT(DISTINCT column1) FROM t;
+    /// ```
+    pub is_distinct: bool,
+    /// The physical expression of arguments the aggregate function takes.
+    pub exprs: &'a [Arc<dyn PhysicalExpr>],
+}
+
 impl AggregateUDF {
     /// Create a new AggregateUDF
     ///
@@ -262,6 +276,13 @@ impl AggregateUDF {
         self.inner.is_descending()
     }
 
+    pub fn value_from_stats(
+        &self,
+        statistics_args: &StatisticsArgs,
+    ) -> Option<ScalarValue> {
+        self.inner.value_from_stats(statistics_args)
+    }
+
     /// See [`AggregateUDFImpl::default_value`] for more details.
     pub fn default_value(&self, data_type: &DataType) -> Result<ScalarValue> {
         self.inner.default_value(data_type)
@@ -574,6 +595,10 @@ pub trait AggregateUDFImpl: Debug + Send + Sync {
     fn is_descending(&self) -> Option<bool> {
         None
     }
+    // Return the value of the current UDF from the statistics
+    fn value_from_stats(&self, _statistics_args: &StatisticsArgs) -> Option<ScalarValue> {
+        None
+    }
 
     /// Returns default value of the function given the input is all `null`.
     ///

datafusion/functions-aggregate/src/count.rs

@@ -16,7 +16,9 @@
 // under the License.
 
 use ahash::RandomState;
+use datafusion_common::stats::Precision;
 use datafusion_functions_aggregate_common::aggregate::count_distinct::BytesViewDistinctCountAccumulator;
+use datafusion_physical_expr::expressions;
 use std::collections::HashSet;
 use std::ops::BitAnd;
 use std::{fmt::Debug, sync::Arc};
@@ -46,14 +48,15 @@ use datafusion_expr::{
     function::AccumulatorArgs, utils::format_state_name, Accumulator, AggregateUDFImpl,
     EmitTo, GroupsAccumulator, Signature, Volatility,
 };
-use datafusion_expr::{Expr, ReversedUDAF, TypeSignature};
+use datafusion_expr::{Expr, ReversedUDAF, StatisticsArgs, TypeSignature};
 use datafusion_functions_aggregate_common::aggregate::count_distinct::{
     BytesDistinctCountAccumulator, FloatDistinctCountAccumulator,
     PrimitiveDistinctCountAccumulator,
 };
 use datafusion_functions_aggregate_common::aggregate::groups_accumulator::accumulate::accumulate_indices;
 use datafusion_physical_expr_common::binary_map::OutputType;
 
+use datafusion_common::utils::expr::COUNT_STAR_EXPANSION;
 make_udaf_expr_and_func!(
     Count,
     count,
@@ -291,6 +294,36 @@ impl AggregateUDFImpl for Count {
     fn default_value(&self, _data_type: &DataType) -> Result<ScalarValue> {
         Ok(ScalarValue::Int64(Some(0)))
     }
+
+    fn value_from_stats(&self, statistics_args: &StatisticsArgs) -> Option<ScalarValue> {
+        if statistics_args.is_distinct {
+            return None;
+        }
+        if let Precision::Exact(num_rows) = statistics_args.statistics.num_rows {
+            if statistics_args.exprs.len() == 1 {
+                // TODO optimize with exprs other than Column
+                if let Some(col_expr) = statistics_args.exprs[0]
+                    .as_any()
+                    .downcast_ref::<expressions::Column>()
+                {
+                    let current_val = &statistics_args.statistics.column_statistics
+                        [col_expr.index()]
+                    .null_count;
+                    if let &Precision::Exact(val) = current_val {
+                        return Some(ScalarValue::Int64(Some((num_rows - val) as i64)));
+                    }
+                } else if let Some(lit_expr) = statistics_args.exprs[0]
+                    .as_any()
+                    .downcast_ref::<expressions::Literal>()
+                {
+                    if lit_expr.value() == &COUNT_STAR_EXPANSION {
+                        return Some(ScalarValue::Int64(Some(num_rows as i64)));
+                    }
+                }
+            }
+        }
+        None
+    }
 }
 
 #[derive(Debug)]

datafusion/functions-aggregate/src/min_max.rs

@@ -15,7 +15,7 @@
 // under the License.
 
 //! [`Max`] and [`MaxAccumulator`] accumulator for the `max` function
-//! [`Min`] and [`MinAccumulator`] accumulator for the `max` function
+//! [`Min`] and [`MinAccumulator`] accumulator for the `min` function
 
 // distributed with this work for additional information
 // regarding copyright ownership.  The ASF licenses this file
@@ -49,10 +49,12 @@ use arrow::datatypes::{
     UInt8Type,
 };
 use arrow_schema::IntervalUnit;
+use datafusion_common::stats::Precision;
 use datafusion_common::{
-    downcast_value, exec_err, internal_err, DataFusionError, Result,
+    downcast_value, exec_err, internal_err, ColumnStatistics, DataFusionError, Result,
 };
 use datafusion_functions_aggregate_common::aggregate::groups_accumulator::prim_op::PrimitiveGroupsAccumulator;
+use datafusion_physical_expr::expressions;
 use std::fmt::Debug;
 
 use arrow::datatypes::i256;
@@ -63,10 +65,10 @@ use arrow::datatypes::{
 };
 
 use datafusion_common::ScalarValue;
-use datafusion_expr::GroupsAccumulator;
 use datafusion_expr::{
     function::AccumulatorArgs, Accumulator, AggregateUDFImpl, Signature, Volatility,
 };
+use datafusion_expr::{GroupsAccumulator, StatisticsArgs};
 use half::f16;
 use std::ops::Deref;
 
@@ -147,6 +149,54 @@ macro_rules! instantiate_min_accumulator {
     }};
 }
 
+trait FromColumnStatistics {
+    fn value_from_column_statistics(
+        &self,
+        stats: &ColumnStatistics,
+    ) -> Option<ScalarValue>;
+
+    fn value_from_statistics(
+        &self,
+        statistics_args: &StatisticsArgs,
+    ) -> Option<ScalarValue> {
+        if let Precision::Exact(num_rows) = &statistics_args.statistics.num_rows {
+            match *num_rows {
+                0 => return ScalarValue::try_from(statistics_args.return_type).ok(),
+                value if value > 0 => {
+                    let col_stats = &statistics_args.statistics.column_statistics;
+                    if statistics_args.exprs.len() == 1 {
+                        // TODO optimize with exprs other than Column
+                        if let Some(col_expr) = statistics_args.exprs[0]
+                            .as_any()
+                            .downcast_ref::<expressions::Column>()
+                        {
+                            return self.value_from_column_statistics(
+                                &col_stats[col_expr.index()],
+                            );
+                        }
+                    }
+                }
+                _ => {}
+            }
+        }
+        None
+    }
+}
+
+impl FromColumnStatistics for Max {
+    fn value_from_column_statistics(
+        &self,
+        col_stats: &ColumnStatistics,
+    ) -> Option<ScalarValue> {
+        if let Precision::Exact(ref val) = col_stats.max_value {
+            if !val.is_null() {
+                return Some(val.clone());
+            }
+        }
+        None
+    }
+}
+
 impl AggregateUDFImpl for Max {
     fn as_any(&self) -> &dyn std::any::Any {
         self
@@ -272,6 +322,7 @@ impl AggregateUDFImpl for Max {
     fn is_descending(&self) -> Option<bool> {
         Some(true)
     }
+
     fn order_sensitivity(&self) -> datafusion_expr::utils::AggregateOrderSensitivity {
         datafusion_expr::utils::AggregateOrderSensitivity::Insensitive
     }
@@ -282,6 +333,9 @@ impl AggregateUDFImpl for Max {
     fn reverse_expr(&self) -> datafusion_expr::ReversedUDAF {
         datafusion_expr::ReversedUDAF::Identical
     }
+    fn value_from_stats(&self, statistics_args: &StatisticsArgs) -> Option<ScalarValue> {
+        self.value_from_statistics(statistics_args)
+    }
 }
 
 // Statically-typed version of min/max(array) -> ScalarValue for string types
@@ -926,6 +980,20 @@ impl Default for Min {
     }
 }
 
+impl FromColumnStatistics for Min {
+    fn value_from_column_statistics(
+        &self,
+        col_stats: &ColumnStatistics,
+    ) -> Option<ScalarValue> {
+        if let Precision::Exact(ref val) = col_stats.min_value {
+            if !val.is_null() {
+                return Some(val.clone());
+            }
+        }
+        None
+    }
+}
+
 impl AggregateUDFImpl for Min {
     fn as_any(&self) -> &dyn std::any::Any {
         self
@@ -1052,6 +1120,9 @@ impl AggregateUDFImpl for Min {
         Some(false)
     }
 
+    fn value_from_stats(&self, statistics_args: &StatisticsArgs) -> Option<ScalarValue> {
+        self.value_from_statistics(statistics_args)
+    }
     fn order_sensitivity(&self) -> datafusion_expr::utils::AggregateOrderSensitivity {
         datafusion_expr::utils::AggregateOrderSensitivity::Insensitive
     }